Putting a new vacuum advance on an engine with internal problems is like a doctor giving a patient aspirin for the headaches caused by a brain tumor. Go ahead and throw parts at the problem if you choose, but I'd "Test, Not Guess" like Sun used to promote. Disconnect and plug the vacuum line if you like, but I've never seen a bad vacuum advance keep an otherwise good engine from running well at low to medium speed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!